Screen For Controlling Sand Production in a Wellbore

ABSTRACT

A wellbore screen ( 1 ) is provided for controlling inflow of solid particles into a wellbore ( 2 ). The wellbore screen comprises a conduit ( 3 ) for transporting fluid, an outer layer ( 4 ) comprising a filter for reducing inflow of solid particles into the conduit ( 3 ), the outer layer extending around the conduit and being radially expandable against the wellbore wall, and swelling means arranged between the conduit and the outer layer. The swelling means ( 6 ) is susceptible of swelling upon contact with a selected fluid so as to radially expand the outer layer against the wellbore wall.

BACKGROUND OF THE INVENTION

The present invention relates to a wellbore screen for controlling inflow of solid particles into a wellbore, the wellbore screen comprising a conduit for transporting fluid and an outer layer comprising a filter for filtering solid particles from fluid flowing into the conduit.

Stand-alone sand exclusion systems, such as slotted liners or a wire-wrapped screens, are generally applied in wells for producing a stream of fluid from the earth formation and wells for injecting a stream of fluid into the earth formation. The produced and/or injected stream of fluid can be, for example, oil, gas or water. A frequently occurring problem in using such sand exclusion system relates to axial flow of fluid in the annular space between the wellbore wall and the screen. Solids from the surrounding formation which flow with the stream of fluid into the wellbore are thereby transported along the screen and deposited as a layer of very low permeability on the screen. The problem is particularly pronounced in case clay particles enter the wellbore. As a result of such flow of fluid through the annular space plugging of the screen potentially takes place over the full length thereof, which may lead to reduced production of hydrocarbon fluid or water from the well. Moreover, if flow of fluid into the screen is reduced to a local section of the screen not (yet) plugged, excessive erosion of the screen may result.

It is an object of the invention to provide an improved wellbore screen which overcomes the aforementioned problems.

In accordance with the invention there is provided a wellbore screen for controlling inflow of solid particles into a wellbore, the wellbore screen comprising a conduit for transporting fluid, an outer layer comprising a filter for reducing inflow of solid particles into the conduit, the outer layer extending around the conduit and being radially expandable against the wellbore wall, and swelling means arranged between the conduit and the outer layer, the swelling means being susceptible of swelling upon contact with a selected fluid so as to radially expand the outer layer against the wellbore wall.

In this manner it is achieved that, after contact of the swelling means with the selected fluid, the outer layer with the filter included is biased against the wellbore wall. Solid particles which locally enter the wellbore are thereby prevented from flowing in longitudinal direction along the entire screen so that the risk of plugging of the entire filter as a result of local inflow of solids is eliminated. Furthermore, the expanded outer layer supports the wellbore wall so that sand failure at the wellbore wall is largely reduced. Moreover the expanded outer layer provides a large inflow area for the screen.

The wellbore can be, for example, a production well for the production of hydrocarbon fluid (crude oil or gas) or water. Alternatively the wellbore can be an injection well for injecting water, oil, gas, waste fluid or another fluid into the earth formation. In either case the selected fluid which causes swelling of the swelling means can be a produced fluid, such as hydrocarbon fluid or water, or an injected fluid such as hydrocarbon fluid (e.g. crude oil, diesel or gas) or water.

In case of a production well for hydrocarbon fluid, fast activation can be achieved by pumping a hydrocarbon fluid, such as diesel, into the wellbore to induce fast swelling of the swelling means. Once fast swelling is achieved, swelling is maintained by virtue of contact of the swelling means with produced hydrocarbon fluid.

It will be understood that in case of an injection well, the problem of plugging can occur during time intervals that injection of fluid is stopped and fluid is allowed to flow back from the wellbore into the screen.

Suitably the swelling means includes a plurality of swelleable rings, each ring extending around the conduit and being susceptible of swelling upon contact with the selected fluid, the rings being mutually spaced along the conduit, for example at regular mutual spacings.

In another arrangement the swelling means includes a sleeve extending around the conduit, the sleeve being provided with a plurality of through-openings spaced along the sleeve, for example through-opening having a substantially rectangular shape or a substantially circular shape.

In a preferred embodiment the swelling means includes a material susceptible of swelling upon contact with hydrocarbon fluid or water.

In case of swelling upon contact with water the material for example is a rubber selected from NBR, HNBR, XNBR, FKM, FFKM, TFE/P or EPDM base rubber.

In case of swelling upon contact with hydrocarbon fluid the material preferably includes a rubber selected from natural rubber, nitrile rubber, hydrogenated nitrile rubber, acrylate butadiene rubber, poly acrylate rubber, butyl rubber, brominated butyl rubber, chlorinated butyl rubber, chlorinated polyethylene, neoprene rubber, styrene butadiene copolymer rubber, sulphonated polyethylene, ethylene acrylate rubber, epichlorohydrin ethylene oxide copolymer, ethylene-propylene-copolymer (peroxide crosslinked), ethylene-propylene-copolymer (sulphur crosslinked), ethylene-propylene-diene terpolymer rubber, ethylene vinyl acetate copolymer, fluoro rubber, fluoro silicone rubber, and silicone rubber.

Preferably said material is selected from EP(D)M rubber (ethylene-propylene-copolymer, either peroxide or sulphur crosslinked), EPT rubber (ethylene-propylene-diene terpolymer rubber), butyl rubber, brominated butyl rubber, chlorinated butyl rubber, and chlorinated polyethylene.

Suitably the outer layer includes an annular filter layer and an annular shroud extending around the annular filter layer.

The invention will be described hereinafter in more detail by way of example, with reference to the accompanying drawings in which:

FIG. 1 schematically shows a longitudinal view in section of an embodiment of a wellbore screen according to the invention, before swelling of the swelling means;

FIG. 2 schematically shows a longitudinal view in section of the embodiment of FIG. 1, after swelling of the swelling means;

FIG. 3 schematically shows cross-section 3-3 of FIG. 1; and

FIG. 4 schematically shows cross-section 4-4 of FIG. 2.

In the Figures like reference signs relate to like components.

Referring to FIGS. 1 and 2 there is shown a wellbore screen 1 arranged in a wellbore 2 for the production of hydrocarbon fluid. The screen 1 comprises a tubular member 3, a permeable annular outer layer 4 extending at a radial distance around the tubular member 3, the outer layer 4 being formed of a filter layer 4 a and a shroud 4 b at the outside of the filter layer 4 a, and a plurality of swelleable elements in the form of rings 6 arranged between the tubular member 3 and the outer layer 4. The rings 6 are arranged at regular spacings along the tubular member 3. The outer layer 4 is flexible and radially expandable to at least an expansion ratio whereby the shroud 4 b contacts the wellbore wall. Furthermore the filter layer 4 a has a sieve opening size adapted to prevent flow of solid particles into the tubular member 3. The rings 6 are made of an elastomer which swells upon contact with hydrocarbon fluid, the elastomer being for example EPDM rubber. The tubular member 3 has a plurality of perforations 7 for inflow of produced hydrocarbon fluid into the tubular member 3, and is at it ends provided with respective connector portions 8, 10 for interconnecting the wellbore screen 1 to a conduit 9 for transporting produced hydrocarbon fluid to surface.

In FIG. 1 is shown the wellbore screen 1 before swelling of the rings 6 upon contact with produced hydrocarbon fluid, so that the outer layer 4 is in its unexpanded state whereby a clearance 11 exists between the shroud 4 b and the wellbore wall.

In FIG. 2 is shown the wellbore screen 1 after swelling of the rings 6 upon contact with hydrocarbon fluid, whereby the outer layer 4 has been radially expanded by the swelling rings 6 so that the annular shroud 4 b contacts the wall of the wellbore 2.

In FIG. 3 is shown the wellbore screen 1 and wellbore 2 in cross-section before swelling of the rings 6. As shown the filter layer 4 a is formed of a plurality of mutually overlapping filter sheets 5. Each filter sheet 5 is at one end thereof connected to one or more of the rings 6 by a respective lug 14, and overlaps with an adjacent filter sheet 5. The shroud 4 b is a thin metal sleeve provided with a mesh of longitudinal slots (not shown) overlapping in longitudinal direction which renders the shroud 4 b extremely flexible to radial expansion while providing adequate protection to the filter layer 4 a.

Referring to FIG. 4 there is shown the wellbore screen 1 and wellbore 2 in cross-section after swelling of the rings 6. The outer layer 4 has been expanded against the wellbore wall, whereby during expansion of the filter layer 4 a sliding of adjacent filter sheets 5 relative each other has occurred, and whereby during expansion of the shroud 4 b widening of the slots of the shroud 4 b has occurred.

For reason of simplicity, in the figures not all rings 6 and perforations 7 are indicated with a reference sign.

During normal use the wellbore screen 1 is lowered into the wellbore 2 and positioned in the hydrocarbon fluid bearing zone of the surrounding formation, whereby the rings 6 are in their respective un-swollen state and the clearance 11 is present between the outer layer 4 and the wall of the wellbore 2 (FIG. 1). When the well 2 is taken in production, a stream of crude oil flows from the surrounding formation into the wellbore 2 and from there via the outer layer 4 and the perforations 7 into the tubular member 3. Thus the stream of hydrocarbon fluid flows along the rings 6 which thereby swell from their unexpanded state (FIG. 1) to their expanded state (FIG. 2). Upon swelling, the rings 6 push in radially outward direction against the outer layer 4 which as a result thereof is expanded against the wall of the wellbore 2. Since the swelling force exerted by the set of rings is distributed along the length of the outer layer 4, the outer layer 4, after expansion thereof, will be substantially compliant with the larger irregularities of the wellbore wall. The sieve opening size of the filter layer 4 a does not change by the radial expansion since during expansion of the filter layer 4 a the individual filter sheets 5 slide relative to each other so that the amount of overlap of adjacent filter sheets 5 decreases. The degree of overlap of adjacent filter sheets 5 is selected so that after expansion of the filter layer 4 a sufficient overlap of the filter sheets 5 remains to ensure that no open spots occur which could allow fluid to bypass the filter layer 4 a.

If desired, accelerated swelling of the rings 6 can be achieved by pumping diesel, or any other suitable fluid, into the wellbore 2 before the well is taken in production.

It is thus achieved that the stream of hydrocarbon fluid is prevented from flowing in axial direction along the outside of the outer layer 4 so that sand or clay particles which may have locally entered into the stream of hydrocarbon fluid, are prevented from flowing in longitudinal direction along the entire outer layer 4. Thus is an important advantage because such flow of particles along the entire outer layer 4 could otherwise lead to plugging of the entire filter layer 4 b, particularly in case of clay particles entering the wellbore.

Additional advantages of the wellbore screen relate to the solid pre-drilled tubular member which has a high collapse resistance, the annular space between the tubular member and the outer layer which provides good inflow characteristics for produced fluid, and the expansion mechanism which obviates the need to mechanically expand the tubular member.

Instead of all rings being made of an elastomer which swells upon contact with hydrocarbon fluid, one or more of the rings can be made of a material which swells upon contact with water produced from the earth formation. For example the rings can include a first set of rings susceptible of swelling in hydrocarbon fluid and a second set of rings susceptible of swelling in water, whereby the rings of the first and second sets are arranged in alternating order.

Furthermore, instead of connecting each filter sheet at one end thereof to some or all of the rings, any other suitable portion of the filter sheet can be connected to the rings. Also the filter sheets can be held in place by the shroud so that there is no need for connecting the filter sheets to some or al of the rings.

As an alternative to the slotted shroud with overlapping longitudinal slots, any other suitable shroud can be used, for example a foldable shroud provided with hinges to allow unfolding of the shroud, or a shroud formed of a plurality of interconnected small tubulars whereby the individual tubulars become flattened upon expansion of the shroud. 

1. A wellbore screen for controlling inflow of solid particles into a wellbore, the wellbore screen comprising a conduit for transporting fluid, an outer layer comprising a filter for reducing inflow of solid particles into the conduit, the outer layer extending around the conduit and being radially expandable against the wellbore wall, and swelling means arranged between the conduit and the outer layer, the swelling means being susceptible of swelling upon contact with a selected fluid so as to radially expand the outer layer against the wellbore wall.
 2. The wellbore screen of claim 1, wherein the swelling means includes a plurality of swelleable rings, each ring extending around the conduit and being susceptible of swelling upon contact with the selected fluid, the rings being mutually spaced along the conduit.
 3. The wellbore screen of claim 2, wherein the rings are arranged at regular mutual spacings along the conduit.
 4. The wellbore screen of claim 1, wherein the swelling means includes a sleeve extending around the conduit, the sleeve being provided with a plurality of through-openings spaced along the sleeve.
 5. The wellbore screen of claim 4, wherein each through-opening has a substantially rectangular shape or a substantially circular shape.
 6. The wellbore screen of claim 1, wherein the swelling means includes a material susceptible to swelling upon contact with hydrocarbon fluid or water.
 7. The wellbore screen of claim 6, wherein said material is susceptible to swelling upon contact with water and includes a rubber selected from Nitrile Butadiene rubber, Hydrogenated Nitrile Butadiene rubber, Carboxylated Nitrile Butadiene rubber, Fluor Polymer, TetraFluorEthylene/PolyPropylene, Ethylene-Propylene-Diene Terpolymer rubber, Chloroprene rubber, ChloroSulfonated Polyethylene, Chlorinated Polyethylene, and PolyUrethane rubber.
 8. The wellbore screen of claim 6, wherein said material is susceptible to swelling upon contact with hydrocarbon fluid and includes a rubber selected from Natural rubber, Acrylate Butadiene rubber, Butyl rubber, Brominated Butyl rubber, Chlorinated Butyl rubber, Chlorinated Polyethylene, Chloroprene rubber, Styrene Butadiene rubber, Sulphonated Polyethylene, Ethylene Acrylate rubber, Epichlorohydrin Ethylene Oxide Copolymer, Epichlorohydrin Ethylene Oxide Terpolymer, Ethylene-Propylene-Copolymer (Peroxide crosslinked), Ethylene-Propylene-Diene Terpolymer rubber, and Silicone rubber.
 9. The wellbore screen of claim 8, wherein said material is selected from Ethylene Propylene Copolymer (Peroxide crosslinked), Ethylene-Propylene-Diene Terpolymer rubber, Butyl rubber, Brominated Butyl rubber, Chlorinated Butyl rubber, and Chlorinated Polyethylene.
 10. The wellbore screen of claim 1, wherein the outer layer includes an annular filter layer and an annular shroud extending around the annular filter layer.
 11. The wellbore screen of claim 1, wherein the wellbore is a wellbore for the production of hydrocarbon fluid or water from the earth formation.
 12. (canceled) 